Transport systems of the above-described type generally have carriages with controlled motors and a rail system provided with specialized mechanical elements which determine the path of the carriage along the track, i.e. whether the carriage will continue in a main direction or will be diverted to a branch.
For example, in such systems, the carriage may normally continue along the straight stretch in the vicinity of a branch unless and until a tongue of the branch is shifted to engage the carriage and divert it along the branch.
Rails with controllable elements of this type, however, have some basic disadvantages. For example, they are comparatively expensive to manufacture and maintain and also necessitate expensive control systems It has been found, moreover, that such arrangements need frequent adjustment and monitoring and that the movable elements at the sites of the respective branch are susceptible to failure and require expensive controls to actuate them.
For example, such movable elements may have to be provided in heated spaces and thus may have to sustain constant heat loads which may be considerable and are detrimental to reliable operation. The same applies, of course, where the track must pass through an aggressive or corrosive atmosphere. In all such cases, special precautions have to be taken to ensure the reliability of trackswitching devices provided along the track and as part thereof.